This invention relates to a method for recovery of oil from tar sands. In particular, it relates to an improved liquid slurry process for recovery of oil from tar sands.
Tar sands, also known as oil or bituminous sands, are sands that are heavily impregnated or saturated with oil. Deposits of these sands are found in many areas of the world including Utah, California, and Alberta, Canada. Although tar sands provide a potentially attractive source of petroleum products, the recovery of valuable components from tar sands in an efficient and economical manner has been a problem. One process for recovery of oil from tar sands is disclosed, for example, in U.S. Pat. No. 2,772,209 and U. S. Pat. No. 3,392,105 comprises adding a diluent to tar sand to form a slurry. The slurry is then heated or introduced into a cyclone as disclosed in U.S. Pat.No. 2,910,424 to achieve separation of oil. One problem encountered by these processes is that tar sand has a high percentage of inorganic solids. The solid particles are of different size ranges so that a complete separation of solids necessitates the use of sophisticated, expensive and energy consuming devices such as centrifuges. A substantially complete removal of solids in a filter zone is impractical because smaller size particles accumulate on the filter restricting the flow rate and resulting in plugging the filter. The expense associated with substantially complete removal of solid particles leads to compromises in the level of solids removed which in turn results in production of oil having high ash content and therefore not suitable for some applications.
One process for the recovery of oil from tar sands includes making a slurry in a melt tank utilizing oil as a solvent. The slurry is then passed to a centrifugal classifier in which it is subdivided into an underflow stream containing coarse sand particles and an overflow stream containing fine sand particles. The underflow stream is passed through a solids removal zone, such as a hot oil filter and the filtrate of that stream combined with the overflow stream is introduced into a coker. The fine sand contained in the combined stream acts as nuclei in coke forming reaction. The coke is removed from the system. The vapors formed in the coking process are condensed and then fed into a fractionator which produces gasoline, naphtha, kerosine, high boiling oil fractions and heavy bottoms. The heavy bottoms and high boiling oil fractions can be recycled from the fractionator to the melt tank.
This invention obviates some of the problems inherent in the processes for recovery of oil from tar sands utilizing oil as a solvent.
Thus, one object of this invention is to provide an improved process for recovery of oil from tar sands.
Another object of this invention is to reduce the size of the equipment used in the process for recovery of oil from tar sands.
A further object of the invention is to reduce the energy requirements in the process for recovery of oil from tar sands.
Still another object of the invention is to recover bitumen contained in the kerosine wash.
Still another object of the invention is to provide for a more efficient reflux in the upper section of the fractionation zone.
Other objects of the invention will become apparent to those skilled in the art upon studying this disclosure.